There is a continuing need for improvements in two-piece hammers for use in hammer mills, shredders and rotary crushers. Such two-piece hammers have a separate hammer shank and a separate replaceable hammer tip. Although such two-piece hammer devices have been known and used widely for a long time, a major drawback in such devices still exists. The major problem resides in the fact that particles of ground material tend to penetrate the joint between the hammer parts and become compacted therein, making it very difficult to separate a worn hammer tip from its shank. This so-called "liming up" of the hammer parts is compounded when the interlocking portions of the hammer pieces include complexly arcuate surfaces such as keys, hinges and forked arms. Abrasion of sharp edges between the hammer parts is an inherent source of ground material which tends to bond the parts under the high operating pressures to which the hammer is normally subjected.
Some designs appear to have encouraged internal abrasion of the hammer parts by purposely allowing room between the hammer tip and the hammer shank for the two to wedge together under operating stress. Past attempts to solve these difficulties have not yielded fully satisfactory results.